There is more scrutiny of the relationship between businessman Ron Medich and the New South Wales Labor Party, after revelations of a political donation to state MP Carmel Tebbutt.

Yesterday the state's Independent Commission Against Corruption announced it will investigate allegations Mr Medich offered a $10,000 bribe in 2009 to Ian Macdonald when he was a minister is the former Labor government.

The ICAC is examining claims the payment was in return for Mr Macdonald arranging meetings where Mr Medich could promote a business he had invested in, electrical supply company Rivercorp.

Mr Macdonald was resources and energy minister at the time.

A donation disclosure document shows Rivercorp donated $4,900 to Ms Tebbutt in 2009, when she was commerce minister.

Another document shows the state's Commerce Department began considering a tender submitted by Rivercorp the next month.

Greens MP John Kaye says there is no suggestion of wrongdoing by Ms Tebbutt, but it shows the dangers of political donations.

"We are not alleging impropriety but she has created the impression of a conflict of interest," Dr Kaye said.

"Mid 2009 was a very busy period for Rivercorp and Mr Medich in developing a close relationship with NSW Labor."

Rivercorp later collapsed.

Ms Tebbutt has rejected the criticism.

"The donation from Rivercorp was fully disclosed in accordance with the law," Ms Tebbutt said.

"I was not involved in the tendering process and at no stage was there any conflict of interest, and I reject any such imputation."

The ICAC will begin its hearings into the allegations involving Mr Macdonald next week.

Mr Medich has been charged with the 2009 murder of Sydney businessman Michael McGurk.

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